Category: Plumbing - Topic: Auto Flushing Toilet
If your toilet suddenly starts flushing itself a second time
and the water re-fills the bowl to a higher point than normal
and automatically flushes itself again,
you might try and replace the flapper inside the fill tank.
It is allowing water to slowly leak into your bowl and when the water level falls
in the tank it refills its self.
Replacing a flapper is reletively easy, and parts come with instructions
from your local hardware and building supply stores.